Martin et al., U.S. Pat. No. 4,058,791, for "Method And Apparatus For Processing Seismic Signals From Low Energy Sources", describes an effort to solve the growing problem of handling information collected in modern seismic surveying in which events of interest could be preserved if only the algebraic signs of the incoming signals (and not the full waveforms) were recorded. Using information channels that need to handle only sign-bits makes it possible to use several times as many channels for the same recording and processing capacity.
Also, Martin et al. observed that in some of their vibratory seismic work, that when sign-bit representations of the source waves were cross-correlated with sign-bit representations of the received waves, the resulting cross-correlation functions appear to be similar to cross-correlation functions from full-waveform inputs, provided that the resulting correlation functions are "common depth point stacked" to a high multiplicity ("the CDP fold is at least 40").
While Martin et al. recognized that high order stacked correlograms of sign-bit data (CDP folds of at least 40) may have acceptable processing qualities to allow their utilization in seismic interpretation, they did not anticipate the special circumstances that single-fold seismic data (or folds where n=`for that matter) could be processed advantageously in a sign-bit form, or more importantly where, in a more general application to seismic processing, the "robust" property of the underlying sign-bit process could be ascertained.
On the general subject of robust modeling, see "Robust Modeling With Erratic Data", J. F. Claerbout and Francis Muir, Geophysics, Vol. 38, No. 5, pp. 826-844, 1973. In the paper, the question of the judicious use of robuts estimators vis-a-vis seismic data is raised but specific applications of such estimators are not discussed, especially in the area of spectral requirements for sign-clipped processing of such data.